<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>promise race</title>
</head>
<body>
    
</body>
<script>
    // race将多个promise实例包装成一个新的promise对象
    //如果多个实例种状态shi'ge'promise实例的状态都为fulfilled，最终结果才能执行.then
    // 如果有一个promise实例的状态为rejected，那么最终结果会执行.catch
    let promise1 = new Promise((resolve,reject)=>{
        setTimeout(()=>{
            resolve(1000)
        },1000)
    }) 

     let promise2 = new Promise((resolve,reject)=>{
        setTimeout(()=>{
            resolve('hello')
        },1000)
    }) 
     let promise3 = new Promise((resolve,reject)=>{
        setTimeout(()=>{
            reject('promise3,失败')
        },1000)
    }) 

     let promise4 = Promise.race([promise1,promise2,promise3])
     .then(res=>{
        console.log(res);
    })
    .catch(err=>{
        console.log(err);
    })
</script>
</html>